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 *   Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
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package org.apache.cayenne.dba.frontbase;

import org.apache.cayenne.CayenneRuntimeException;
import org.apache.cayenne.DataRow;
import org.apache.cayenne.access.DataNode;
import org.apache.cayenne.access.OperationObserver;
import org.apache.cayenne.access.util.DoNothingOperationObserver;
import org.apache.cayenne.dba.JdbcAdapter;
import org.apache.cayenne.dba.JdbcPkGenerator;
import org.apache.cayenne.map.DbEntity;
import org.apache.cayenne.query.Query;
import org.apache.cayenne.query.SQLTemplate;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * @since 1.2
 */
public class FrontBasePkGenerator extends JdbcPkGenerator {

	public FrontBasePkGenerator(JdbcAdapter adapter) {
		super(adapter);
		pkStartValue = 1000000;
	}

	/**
	 * Returns zero as PK caching is not supported by FrontBaseAdapter.
	 */
	@Override
	public int getPkCacheSize() {
		return 0;
	}

	@Override
	public void createAutoPk(DataNode node, List<DbEntity> dbEntities) throws Exception {
		// For each entity (re)set the unique counter
		for (DbEntity entity : dbEntities) {
			runUpdate(node, pkCreateString(entity.getName()));
		}
	}

	@Override
	public List<String> createAutoPkStatements(List<DbEntity> dbEntities) {
		List<String> list = new ArrayList<>();
		for (DbEntity entity : dbEntities) {
			list.add(pkCreateString(entity.getName()));
		}
		return list;
	}

	@Override
	public void dropAutoPk(DataNode node, List<DbEntity> dbEntities) throws Exception {
	}

	@Override
	protected String pkTableCreateString() {
		return "";
	}

	@Override
	protected String pkDeleteString(List<DbEntity> dbEntities) {
		return "-- The 'Drop Primary Key Support' option is unavailable";
	}

	@Override
	protected String pkCreateString(String entName) {
		StringBuilder buf = new StringBuilder();
		buf.append("SET UNIQUE = ").append(pkStartValue).append(" FOR \"").append(entName).append("\"");
		return buf.toString();
	}

	@Override
	protected String pkSelectString(String entName) {
		StringBuilder buf = new StringBuilder();
		buf.append("SELECT UNIQUE FROM \"").append(entName).append("\"");
		return buf.toString();
	}

	@Override
	protected String pkUpdateString(String entName) {
		return "";
	}

	@Override
	protected String dropAutoPkString() {
		return "";
	}

	/**
	 * @since 3.0
	 */
	@Override
	protected long longPkFromDatabase(DataNode node, DbEntity entity) throws Exception {

		String template = "SELECT #result('UNIQUE' 'long') FROM " + entity.getName();

		final long[] pkHolder = new long[1];

		SQLTemplate query = new SQLTemplate(entity, template);
		OperationObserver observer = new DoNothingOperationObserver() {

			@Override
			public void nextRows(Query query, List<?> dataRows) {
				if (dataRows.size() != 1) {
					throw new CayenneRuntimeException("Error fetching PK. Expected one row, got %d", dataRows.size());
				}

				DataRow row = (DataRow) dataRows.get(0);
				Number pk = (Number) row.get("UNIQUE");
				pkHolder[0] = pk.longValue();
			}
		};

		node.performQueries(Collections.singleton((Query) query), observer);
		return pkHolder[0];
	}
}